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<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Dear Paul<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Philip is correct, of course, and lays it out quite clearly, lest there remain is life in that dead thing.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">></span>Please provide the equation that puts char (that is, the energy in the char) above the line in a way that recognizes that it is not a loss of energy, it is only a transformation of the energy that
is in the fuel.<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Two things, a formula, and a correction: it is
<i>not</i> a transformation of energy, it is a transformation of the fuel, retaining the energy.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">This it has been proposed that the energy in the char be referred to as ‘retained energy’ because that is exactly what it is – energy that was present in the input fuel and retained in the charred resultant
fuel. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">The energy that is lost is gone.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">The energy that is in the pot is ‘useful’.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">The energy in the residual fuel (which could be char) is energy retained.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">If the recoverable char (which is a fraction of the whole of the residual fuel and in turn a fraction of the total char) is to be reported, it has two prime characteristics:
<o:p></o:p></span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="color:windowtext;margin-left:0cm;mso-list:l0 level1 lfo1">
its mass expressed as a fraction of the dry mass of fuel that was put in, and <o:p>
</o:p></li><li class="MsoListParagraph" style="color:windowtext;margin-left:0cm;mso-list:l0 level1 lfo1">
the energy retained in that char expressed as a fraction of the input energy.<o:p></o:p></li></ul>
<p class="MsoNormal"><br>
<span style="color:windowtext">There are three things of interest when talking about a char-making stove:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Energy lost<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Energy applied to a heating task<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Energy retained in the residual fuel, whether or not that is the total energy or the energy in the “recoverable char” fraction of it.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">It would be helpful if the conversation used the more precise language we used when examining this question. “Char” is not everything left after a burn. It is
<i>some</i> of what is left. It is in fact an indeterminate fraction because a) there may be some or none and b) it is not clear how to define ‘recoverable’.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Talking about char on a mass basis presents a slight problem when it comes to a precise meaning because the ash content is indeterminate. Just because a fuel has a known input char % mass, that does not mean
that the char contains all of it, nor does it mean it is in the char contains ash ‘evenly’, i.e. homogeneously through the bulk of the char. The top char from a TLUD may have much more as a % of mass than ‘bottom char’.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">If the char is being buried in the ground, the energy content is immaterial. If the char is being used as a fuel (there are gasifier stoves that can use the last session’s charred wood pellets mixed with new
pellets) then the energy content is important because it has to be known so that the next calculation has the correct value in the denominator.
<o:p></o:p></span></p>
<p class="MsoNormal"><br>
<span style="color:windowtext">Paul: After lengthy discussion about fuel v.s. energy, the conclusion was that ‘fuel’ is a proxy term for energy. When constructing a test protocol from first principles, we agreed that the term fuel really meant the energy it
contained. </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext">Crispin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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